GPS disrupters really wouldn't harm commercial aviation all that much.
Most of the LNAV that commercial airliners use is still largely based off of intertial reference systems. The FMS computer uses a cross check of DME data from VORTACS and, if installed on the aircraft, cross checks against the GPS signal.
So if your IRS units fail, it'll revert to GPS and DME. If your GPS unit fails, it'll still reference the IRU's (primarily) and then cross check with DME data.
Heck, in some of the older MD-88's, the FMS is just nothing more than a super-dooper RNAV that simply references DME triangulation and nothing more (AHRS).
Nothing like a little AHRS map shift to start off the morning!
Umm, I guess I'm guilty of thread creep, went WAAAY off-topic and probably provided WAAAY too much information, but there ya have it!